Four more headline acts have been announced for the 2013 Open’er Festival, which takes place in Gdynia, Poland, on July 3-6.

Doomy stadium-indie types Editors (pictured), Mercury Prizewinners Alt-J, Britpop survivors Skunk Anansie and the perennially popular Modest Mouse have all been added to the A-list bill, for which Rihanna, Blur, Kings Of Leon, Arctic Monkeys, Animal Collective, Queens Of The Stone Age, Tame Impala, Disclosure and Maria Peszek have already been announced.

There are many more acts still to be announced; full 4-day camping tickets are currently available for just £93. For more information and tickets, click here.